Tiedback walls are commonly used as permanent earth retaining structures. In one known construction, the wall is built by first installing a plurality of laterally spaced soldier beams in the earth along a predetermined position of the wall to be constructed. The soldier beams may have various shapes and usually are either drilled or driven place. Earth is excavated adjacent the soldier beams to a designated depth and temporary earth retaining apparatus, such as lagging, is installed between the soldier beams against the exposed face of the earthen mass. The excavating and lagging installation steps are repeated until the tieback location is reached. A plurality of tiebacks is installed and anchored in the earthen mass and connected to the soldier beams. The excavating and tieback installation steps are repeated as necessary. When the location for the bottom of the wall is reached, precast concrete panels are attached to the soldier beams, or a reinforced concrete face made from cast-in-place concrete may be used.
The soldier beams, the connections between the soldier beams and the tiebacks, and the connections between the precast concrete panels and the soldier beams are located in a potentially corrosive environment, since both oxygen and groundwater are likely to be present. In the past, the soldier beams and these connections have been protected from corrosion by using coatings, galvanizing, or concrete encasement. However, these methods have numerous drawbacks. Most coatings on the soldier beams are damaged during the process of driving the soldier beams into the earthen mass. The coatings on the soldier beams in the vicinity of the connections and the coatings on the connection pieces must be removed in order to weld the connections to the soldier beam. In order to make the coatings effective, they must be repaired wherever they were damaged or removed. This procedure is expensive and it frequently does not result in an adequate coating. Galvanizing the soldier beam and the connections is difficult and is very expensive. Facilities with galvanizing tanks long enough to accommodate the soldier beams, often 50 feet long, are not readily available. Field cutting and welding of galvanized steel is difficult and the area affected by the cutting and welding must be field coated which is not very effective. Concrete encasement of the soldier beam-tieback connections and the soldier beam-panel connections is accomplished by completely filling the space between the panels, the soldier beams, and the temporary earth retaining apparatus with concrete along the entire length of the wall. If this space is completely filled, a large quantity of concrete is required and a separate drainage means must be provided behind the wall to prevent hydrostatic pressure from building up behind the panels. This increases the cost of constructing the earth retaining wall.
Prior art walls require either draining water under the wall through a pipe or draining water through the wall. The former method involves collecting the water behind the wall using a drainage material and discharging the water through a pipe located behind or in front of the wall. The latter method is accomplished by collecting the water behind the wall and discharging the water through the face of the wall either by drilling weep holes through the concrete wall in the field or prefabricating weep holes in the wall. These are expensive procedures.